Trading bug?

I noticed a strange trade in PM.2014.NATIONAL that took place at 00:42:38 on August 7. 100 shares changed hands at $0.4537, but trading prices on either side of that trade were well above $0.80. I know for sure that there were many buy orders between $0.80 and $0.4537, including one of my own. I'm just wondering why this trade could take place without the higher buy orders being fulfilled first.

I'm relatively new here, I hope I don't have a fundamental misunderstanding to how trading works here.

It was probably the result of someone buying a bundle of stocks PM.2014.LABOUR, PM.2014.NATIONAL, PM.2014.OTHER.

When a bundle is bought for $1 the prices for the individual stocks in the bundle seem to be calculated based on their last trade prices, scaled to make the total $1. The unusual trade you saw was probably the result of someone buying a bundle when the last trade price of PM.2014.OTHER was unusually high. (There has been some very strange trading on PM.2014.OTHER recently).

E.g. If the last trade prices were: LABOUR $0.30, NATIONAL $0.70, OTHER $0.50, then buying a bundle would result in three trades recorded as LABOUR $0.2000, NATIONAL $0.4667, OTHER $0.3333 for a total of $1.

Ah, of course. I checked PM.2014.OTHER and it was indeed very high on Aug 7. Thanks for the explanation!